Generally speaking, a main shaft of a spinning wheel type fishing reel can move back and forth under the drive of a machine body assembly, but cannot rotate, a drag system is arranged between a line spool and the main shaft, and the line spool can move back and forth under the drive of the main shaft. During take-up, a pressure needs to be applied to the drag system via a drag knob assembly to increase the rotation resistance of the line spool, and the line spool cannot rotate within a certain stress range, so that the take-up function is satisfied. During pay-off, the pressure applied to the drag system needs to be reduced via the drag knob assembly to reduce the rotation resistance of the line spool, so that the line spool can freely rotate to guarantee to freely release a fishing line under certain tension.
The existing drag knob assembly structure available on the market cannot indicate the rotation angle of the drag knob assembly, so that the size of the resistance applied to the line spool cannot be determined, in this case, the drag knob assembly structure is poor in force adjustment accuracy and is inconvenient to use.